_Dichotomies and Categories versus Dimensions_ **The inherent difficulty is when people try to create categories, and artificially create seperation. Instead, behavior or personality or anything should be view as a continuum.** - The difficulty inherent in the _DSM_ conception of psychopathology and other attempts to distinguish between normal and abnormal or adaptive and maladaptive is that they are _dichotomous_ or _categorical models_ that attempt to describe guidelines for clearly distinguishing between individuals who are normal or abnormal and for determining which specific abnormality or “disorder” a person has. An alternative model, overwhelmingly supported by research, is the _dimensional model_. In the dimensional model, normality and abnormality, as well as effective and ineffective psychological functioning, lie along a continuum; so-called psychological disorders are simply extreme variants of normal psychological phenomena and ordinary problems in living (Keyes & Lopez, 2002; Widiger, this volume). The dimensional model is concerned not with classifying people or disorders but with identifying and measuring individual differences in psycho- logical phenomena such as emotion, mood, intelligence, and personality styles (e.g., Lubinski, 2000). Great differences among individuals on the dimensions of interest are expected, such as the differences we find on standardized tests of intelligence. As with intelligence, divisions between normality and abnormality may be demarcated for convenience or efficiency but are not to be viewed as indicative of true discontinuity among “types” of phenomena or “types” of people. Also, statistical deviation is not viewed as necessarily pathological, although extreme variants on either end of a dimension (e.g., introversion-extraversion, neuroticism, intelligence) may be maladaptive if they lead to inflexibility in functioning. - Empirical evidence for the validity of a dimensional approach to psychological adjustment is strongest in the area of personality and personality disorders (Costello, 1996; Maddux & Mundell, 1999; Coker & Widiger, this volume). Factor analytic studies of personality problems among the general population and clinical populations with “personality disorders” demonstrate striking simi- larity between the two groups. In addition, these factor structures are not consistent with the _DSM_’s system of classifying disorders of personality into categories (Maddux & Mundell, 1999) and sup- port a dimensional rather than a categorical view. For example, the most recent evidence strongly suggests that psychopathic personality (or antisocial personality) and other externalizing disorders of adulthood display a dimensional structure, not a categorical structure (Edens, Marcus, Lilienfeld, & Poythress, 2006; Krueger, Markon, Patrick, & Iacono, 2005; Larsson, Andershed, & Lichtenstein, 2006). The dimensional view of personality disorders also is supported by cross-cultural research (Alarcon, Foulks, & Vakkur, 1998). - Research on other problems supports the dimensional view. Studies of the varieties of normal emo- tional experiences (e.g., Oatley & Jenkins, 1992) indicate that “clinical” emotional disorders are not discrete classes of emotional experience that are discontinuous from everyday emotional upsets and problems. Research on adult attachment patterns in relationships strongly suggests that dimensions are more useful descriptions of such patterns than are categories (Fraley & Waller, 1998). Research on self-defeating behaviors has shown that they are extremely common and are not by themselves signs of abnormality or symptoms of “disorders” (Baumeister & Scher, 1988). Research on children’s read- ing problems indicates that “dyslexia” is not an all-or-none condition that children either have or do not have but occurs in degrees without a natural break between “dyslexic” and “nondyslexic” children (Shaywitz, Escobar, Shaywitz, Fletcher, & Makuch, 1992). Research on attention deficit/hyperactivity (Barkley, 1997) and posttraumatic stress disorder (Anthony, Lonigan, & Hecht, 1999) demonstrates this same dimensionality. Research on depression and schizophrenia indicates that these “disorders” are best viewed as loosely related clusters of dimensions of individual differences, not as diseaselike syndromes (Claridge, 1995; Costello, 1993a, 1993b; Persons, 1986). For example, a study on depres- sive symptoms among children and adolescents found a dimensional structure for all of the _DSM-IV_ symptoms of major depression (Hankin, Fraley, Lahey, & Waldman, 2005). The inventor of the term _schizophrenia_, Eugene Bleuler, viewed so-called pathological conditions as continuous with so-called normal conditions and noted the occurrence of “schizophrenic” symptoms among normal individuals (Gilman, 1988). In fact, Bleuler referred to the major symptom of “schizophrenia” (thought disorder) as simply “ungewonlich,” which in German means “unusual,” not “bizarre,” as it was translated in the first English version of Bleuler’s classic monograph (Gilman, 1988). Essentially, the creation of “schizo- phrenia” was “an artifact of the ideologies implicit in nineteenth century European and American medical nosologies” (Gilman, 1988, p. 204). Indeed, research indicates that the hallucinations and delusions exhibited by people diagnosed with a schizophrenic disorder are continuous with experi- ences and behaviors among the general population (Johns & van Os, 2001; see also Walker, Bollini, Hochman, & Kestler, this volume). Finally, biological researchers continue to discover continuities between so-called normal and abnormal (or pathological) psychological conditions (Claridge, 1995; Livesley, Lang, & Vernon, 1998).